Biochemical Characterization of a GDSL-Motif Esterase from Bacillus sp. K91 with a New Putative Catalytic Mechanism

( Jun Mei Ding ),( Ting Ting Yu ),( Lian Ming Liang ),( Zhen Rong Xie ),( Yun Juan Yang ),( Jun Pei Zhou ),( Bo Xu ),( Jun Jun Li ),( Zun Xi Huang ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.11

The esterase gene Est8 from the thermophilic bacterium Bacillus sp. K91 was cloned and expressed in Escherichia coli. The monomeric enzyme exhibited a theoretical molecular mass of 24.5 kDa and an optimal activity around 50°C at pH 9.0. A model of Est8 was constructed using a hypothetical YxiM precursor structure (2O14_A) from Bacillus subtilis as template. The structure showed an α/β-hydrolase fold and indicated the presence of a typical catalytic triad consisting of Ser-11, Asp-182, and His-185, which were investigated by site directed replacements coupled with kinetic characterization. Asp-182 and His-185 residues were more critical than the Ser-11 residue in the catalytic activity of Est8. A comparison of the amino acid sequence showed that Est8 could be grouped into the GDSL family and further classified as an SGNH hydrolase. Est8 is a new member of the SGNH hydrolase subfamily and may employ a different catalytic mechanism.

New Technique of Seeding Chondrocytes into Microporous Poly(L-lactide-co-ε-caprolactone) Sponge by Cyclic Compression Force-Induced Suction

Xie, Jun,Jung, Youngmee,Kim, Soo Hyun,Kim, Young Ha,Matsuda, Takehisa Mary Ann Liebert 2006 Tissue engineering Vol.12 No.7

<P>The initial requirement for a functional engineered cartilage tissue is the effective and reproducible seeding of chondrocytes into the interior of microporous scaffolds. High seeding efficiency, high cell viability, uniform cell distribution, and short operation time are also essential. We devised a new technique of seeding rabbit chondrocytes into microporous poly(L-lactide-co-epsilon-caprolactone) (PLCL) (porosity, 71- 80%; wall thickness, 2 and 6 mm) sponges under compression force-induced suction using a custom designed loading apparatus. Cell distribution and cell viability were determined using confocal laser scanning microscopy with fluorescent dye-staining techniques. Factors that affect the quality of a cell seeded construct were studied, namely, the porosity and thickness of sponges and suction cycles. Under 1 cycle of suction, an increase in porosity promoted cell seeding efficiency (CSE; defined as the percentage of the number of cells in the sponges relative to the initial number of cells seeded), cell viability (at 1 day post seeding), and a relatively uniform cell distribution, whereas thick sponges exhibited an inhomogeneous cell distribution irrespective of incubation time. Multiple cycles of suction of 5 and 10 at 0.1 Hz significantly improved the CSE, whereas high cell viability was maintained and even spatial cell distribution was achieved in 1 week. This study revealed that our newly developed cell seeding technique with multiple cycles of suction is a promising approach to inoculating cells into microporous sponges with high CSE, high cell viability, and homogeneous cell distribution.</P>

Mechano-Active Scaffold Design Based on Microporous Poly(L-lactide-co-<i>ε</i>-caprolactone) for Articular Cartilage Tissue Engineering: Dependence of Porosity on Compression Force-Applied Mechanical Behaviors

Xie, Jun,Ihara, Maki,Jung, Youngmee,Kwon, Il Keun,Kim, Soo Hyun,Kim, Young Ha,Matsuda, Takehisa Mary Ann Liebert 2006 Tissue engineering Vol.12 No.3

<P>An essential component of functional articular cartilage tissue engineering is a mechano-active scaffold, which responds to applied compression stress and causes little permanent deformation. As the first paper of a series on mechano-active scaffold-based cartilage tissue engineering, this study focused on mechanical responses to various modes of loading of compression forces and subsequent selection of mechano-active scaffolds from the biomechanical viewpoint. Scaffolds made of elastomeric microporous poly(L-lactide-co-epsilon-caprolactone) (PLCL) with open-cell structured pores (300 approximately 500 microm) and with different porosities ranging from 71 to 86% were used. The PLCL sponges and rabbit articular cartilage tissue were subjected to compression/unloading tests (0.1 and 0.005 Hz) at 5 kPa, and stress relaxation tests at 10, 30, and 50% strain. The measurements of the maximum strain under loading and residual strain under unloading for compression tests and the maximum stress and equilibrium stress in the stress relaxation test showed that the lower the porosity, the closer the mechanical properties are to those of native cartilage tissue. Among the PLCL sponges, the sponge with 71% porosity appears to be a suitable cartilage scaffold.</P>

关系视角下的经理人反馈寻求行为:心理预期和政治技能的影响

Xie Jun,Wang Lin,Chu Xiaoping 성균관대학교 현대중국연구소 2014 성균관대학교 현대중국연구소 국제학술회의 Vol.- No.20

Organizations today are facing an increasingly global and competitive marketplace, and so they, as well as their managers must be adaptable to survive. As strategic changes become more frequent, managers face a higher level of wicertainty and complety in the workplace. These factors combined suggest that managers will need to proactively seek out feedback to adequately adapt and perform. However, discussions about what factors and how they affect managers' feedback-seeking behavior in Chinese context are rare. In this study, we investigate the intrinsic mechanisms of how the indigenous Chinese construct supervisor-subordinate guanxi influences managers' feedback-seeking behavior. Supervisor-Subordinate guanxi is defined as a dyadic, particular and sentimental tie that has potential of facilitating favor exchanges between the parties connected by the tie. This concept includes affective attachment, personal-life inclusion, and deference to supervisor. Although studies have suggested that Chinese supervisors have extensive control over resources and can impact employees' lives in various ways, evidence regarding the intermediate psychological processes that would explain how and why supervisor-subordinate guanxi affects managers' feedback-seeking behavior remains inconclusive and underdeveloped' Drawing from two theoretical perspectives in the feedback seeking literature, the efficiency-oriented perspective and impression-management perspective, we examine the mediation effects of managers' performance-enhancement expectations and impression-management expectations. Further, consistent with recent calls for the examination of moderators for feedback seeking behavior, political skill was included so we could examine its interplay with supervisor subordinate guanxi on managers' feedback-seeking behavior. Analyses based on dyad samples in family business from Guangdong province show that: (1) supervisor subordinate guanxi is positively related to managers' feedback-seeking behavior; (2) performance-enhancement expectations and impression-management expectations partially mediated supervisor-subordinate guanxi' s influence on managers' feedback-seeking behavior; (3) p이1tical skill positively moderated the relationships between supervisor-subor이nate guanxi and managers' feedback-seeking behavior in such a way that the relationships were stronger for individuals higher than lower in political skill. Our research contributes to the feedback seeking literature by answering how and why supervisor-subordinate guanxi is related to managers' feedback-seeking behabvior in Chinese context. Managerial implications and limitations of the study are discussed.

Mechanical Loading-Dependence of mRNA Expressions of Extracellular Matrices of Chondrocytes Inoculated into Elastomeric Microporous Poly(L-lactide-co-<i>ε</i>-caprolactone) Scaffold

Xie, Jun,Han, Zhiyi,Kim, Soo Hyun,Kim, Young Ha,Matsuda, Takehisa Mary Ann Liebert, Inc 2007 Tissue engineering Vol.13 No.1

Highly Reliable White LEDs Using Nitride Phosphors

Xie, Rong-Jun,Hirosaki, Naoto,Takeda, Takashi The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.4

Nitride phosphors are now attracting significant attention of material scientists and phosphor engineers, because they promise red-shifted photoluminescence spectra, small Stokes shift, high quantum efficiency and low thermal degradation. A number of interesting nitride phosphors have been developed and practiced for producing white light with LED chips. In this paper, the applications of nitride phosphors in highly reliable wLEDs will be overviewed.

Saliva Supernatant miR-21: a Novel Potential Biomarker for Esophageal Cancer Detection

Xie, Zi-Jun,Chen, Gang,Zhang, Xu-Chao,Li, Dong-Feng,Huang, Jian,Li, Zi-Jun Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.12

Objective: To identify whether saliva supernatant miR-21 can serve as a novel potential biomarker in patients with esophageal cancer (EC). Methods: 32 patients with EC and 16 healthy controls were recruited in this study. Total RNA was extracted from saliva supernatant samples for measurement of miR-21 levels using RT-qPCR and relationships between miR-21 levels and clinical characteristics of EC patients were analyzed. Results: miR-21 was significantly higher in the EC than control groups. The sensitivity and specificity were 84.4% and 62.5% respectively. Supernatant miR-21 levels showed no significant correlation with cancer stage, differentiation and nodal metastasis. Conclusions: Saliva supernatant miR-21 may be a novel biomarker for EC.

Effects of astaxanthin on antioxidant capacity of golden pompano (Trachinotus ovatus) in vivo and in vitro

Xie, Jia-jun,Chen, Xu,Niu, Jin,Wang, Jun,Wang, Yun,Liu, Qiang-qiang The Korean Society of Fisheries and Aquatic Scienc 2017 Fisheries and Aquatic Sciences Vol.20 No.4

The objective of this research was to study the effect of astaxanthin (AST) on growth performance and antioxidant capacity in golden pompano (Trachinotus ovatus) both in vivo and in vitro. In the in vivo study, two diets were formulated with or without astaxanthin supplementation (D1 and D2; 0 and 200 mg/kg) to feed fish for 6 weeks. In the in vitro study, cells from hepatopancreas of golden pompano were isolated and four treatments with or without astaxanthin and $H_2O_2$ supplementation were applied (control group: without both astaxanthin and $H_2O_2$ treated; $H_2O_2$ group: just with $H_2O_2$ treated; $H_2O_2$ + AST group: with both astaxanthin and $H_2O_2$treated; AST group: just with AST treated). Results of the in vivo study showed that weight gain (WG) and special growth rate (SGR) significantly increased with astaxanthin supplemented (P < 0.05). Feed conversion ratio (FCR) of fish fed D2 diet was significantly lower than that of fish fed D1 diet (P < 0.05). Hepatic total antioxidant capacity (T-AOC) and the reduced glutathione (GSH) of golden pompano fed D2 diet were significant higher than those of fish fed D1 diet (P < 0.05). Superoxide dismutase (SOD) was significantly declined as astaxanthin was supplemented (P < 0.05). Results of the in vitro study showed that the cell viability of $H_2O_2$ group was 52.37% compared to the control group, and it was significantly elevated to 84.18% by astaxanthin supplementation ($H_2O_2$ + AST group) (P < 0.05). The total antioxidant capacity (T-AOC) and the reduced glutathione (GSH) of cell were significant decreased by oxidative stress from $H_2O_2$ (P < 0.05), but it could be raised by astaxanthin supplementation ($H_2O_2$ vs $H_2O_2$ + AST), and the malondialdehyde (MDA) was significant higher in $H_2O_2$ group (P < 0.05) and astaxanthin supplementation could alleviate the cells from lipid peroxidation injury. In conclusion, dietary astaxanthin supplementation can improve the growth performance of golden pompano. Moreover, astaxanthin can improve the golden pompano hepatic antioxidant capacity both in vivo and in vitro study by eliminating the reactive oxygen species.

Articular cartilage tissue engineering based on a mechano-active scaffold made of poly(L-lactide-co-ϵ-caprolactone): In vivo performance in adult rabbits

Xie, Jun,Han, Zhiyi,Naito, Masatoshi,Maeyama, Akira,Kim, Soo Hyun,Kim, Young Ha,Matsuda, Takehisa Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of Biomedical Materials Research Part B Vol. No.

<P>Our previous studies showed that a mechano-active scaffold made of poly(L-lactide-co-ϵ-caprolactone) (PLCL) exhibited a high potential to realize the formation of a functional, engineered cartilage in vitro. This animal study therefore was designed to investigate the feasibility of repairing on osteochondral defect with the use of bone marrow-derived mesenchymal stem cells (BMSCs) incorporated with a PLCL scaffold. Rabbit BMSCs, isolated and subsequently cultured in monolayer, were seeded into a porous PLCL scaffold sponge following an implantation onto a full-thickness osteochondral defect (diameter of 4.5 mm, depth of 5 mm) that was artificially created on the medial femoral condyles at a high load-bearing site on a rabbit's knee joint. Time-dependent healing of the defect was evaluated by macroscopic, histological examinations at both 3- and 6-month-implantations, respectively. A PLCL sponge incorporated with BMSCs exhibited sufficient structural support, resulting in new osteochondral tissue regeneration: a physiologically well-integrated subchondral bone formation, a hyaline cartilage-like morphology containing chondrocytes surrounded by abundant cartilaginous matrices. In addition, quantitative biochemical assays also demonstrated high potential for the synthesis of sulfated glycosaminoglycan and collagen, both of which are biomolecules essential to extracelluar matrix in normal cartilage tissue. In contrast, defects filled with cell-free PLCL scaffold or left empty showed a very limited potential for regeneration. Our findings suggest that a composite of PLCL-based sponge scaffold and BMSCs promote the repair of osteochondral defects at high load-bearing sites in adult rabbits. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010</P>

Numerical Study on Rotating Characteristics of Unsteady Flow Inner Pump-turbine in Pump Mode

Jun Yang,Tian Xie,Pavesi Giorgio,Xiaohua Liu,Jun Liu 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.3

In order to investigate the formation of the rotating stall in diffuser of pump-turbine in pump mode, the unsteady flow with radial rotating characteristics before the occurrence of rotating stall are investigated by detached eddy simulation. The results indicate that the unsteady flow patterns which occur in the return channel both at full and part load conditions contain two periodical disturbances with frequencies St≈0.042 and St≈0.085, and the Strouhal number St is frequency normalized by blade passing frequency of impeller. These periodical disturbances not only influence the pressure field but also cause rotating characteristics in diffuser channels. One is composed of 4 cells propagating at 0.073 times of impeller rotating speed. The other one is made up of 3 rotating cells with 0.2 times of backward impeller rotating speed. Meanwhile, there are two radial rotating characteristics which contribute the spectra peak at blade pass frequency in diffuser. One is at the inlet of diffuser propagating at impeller rotating speed with 7 cells, and the other one contains 4 cells with about 1.75 backward impeller rotating speed.